Results 21 to 30 of about 8,452 (119)
Conservation Biology, Volume 40, Issue 4, August 2026.Abstract Knowledge of species distributions is essential for informing policies on nature conservation and restoration. However, updating them on a regular basis and doing so in a harmonized manner at the international level is difficult. The European Bird Census Council integrated national monitoring data covering 5 years to update farmland bird ...
Sergi Herrando +54 more
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Uncovering correlates of decline and critical refuges for a threatened terrestrial mammal
Conservation Biology, Volume 40, Issue 4, August 2026.Abstract Globally, the geographic ranges of numerous species are contracting. Identifying spatiotemporal patterns of threat impact can illuminate why species decline in some parts of their range but persist in others. We developed a correlative approach to identify species’ response thresholds and locate ecological refuge areas associated with ...
Natalya M. Maitz +5 more
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Jixie chuandong, 1998 摆线针轮行星减速机的传动误差是其内部各零部件的制造误差、装配误差和修形原理误差的函数。运用齿轮啮合原理 ,从减速机的制造过程和装配过程出发 ,可以建立较符合工程实际的数学模型并进而推导出减速机传动误差的解析计算方法。通过单因素分析 ,可以了解各种单项制造误差因素对减速机传动误差的影响程度。通过对传动误差进行统计计算 ,可以对减速机的优化设计 ...
姚文席
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The Photogrammetric Record, Volume 41, Issue 195, July‐September 2026.Tri‐stereoscopic PeruSat‐1 imagery enables the simultaneous generation of 0.70 m‐resolution topography and spatially distributed Manning roughness maps, achieving 0.434 m vertical accuracy. Integrated into HEC‐RAS, these products provide consistent, high‐resolution inputs that improve hydraulic modelling and flood risk assessment in data‐scarce river ...
Jorge L. Miranda‐Pita +3 more
wiley +1 more source
Jixie chuandong, 1992 本文用三维有限元——数学规划方法,分析了窄斜齿轮在误差条件下的三维接触状况,包括压力角误差、螺旋角误差、基节误差、齿轮修形、以及由于齿轮支承变形引起的啮合误差的影响,进一步分析了误差存在时载荷大小对接触状态的影响。通过计算得到各种情况下的齿面载荷分布和齿轮副的振动激励——传动误差,为斜齿轮传动的动、静强度分析提供了可靠的依据。
方宗德, 沈允文
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World Water Policy, Volume 12, Issue 1, February 2026.ABSTRACT Urban expansion significantly impacts flood risk, particularly in rapidly growing areas where impervious surfaces exacerbate surface runoff. This study examines spatial patterns of urban growth and their effects on flood exposure in Mecklenburg County, North Carolina, from 2011 to 2021.
Pegah Madadi, Azad Sadeghi
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基于高斯混合模型 Varian NovalisTX 直线加速器盆腔肿瘤放疗摆位误差分布预测模型的构建
Zhongshan Daxue xuebao. Yixue kexue ban, 2019 【目的】构建 Varian NovalisTX 直线加速器盆腔肿瘤放疗摆位误差分布预测模型。【方法】选取加速器 治 疗 30 例 盆 腔 肿 瘤 患 者 先 验 IGRT 摆 位 误 差 数 据 ，采 用 高 斯 混 合 模 型 构 建 误 差 分 布 预 测 模 型 ，并 求 解 分 析 模 型 参数。【结果】由模型参数可知摆位误差主要往μ1~μ4 四个中心点方向集中；中心点坐标表明误差在 Vrt 方向（-3.88~4.28）mm 和 Lng 方 向（-2.41~1.54）mm 较 大 ，Lat 方 ...
丘敏敏 +4 more
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Gaoya dianqi, 2020 随着特高压工程的推进,CT现场校验成为亟需解决的难题。由于国内外对此问题研究尚属空白,为解决该难题,提出将实验室CT校验用的自校法应用于现场交接试验。在解决了一系列自校法工程应用问题的基础上,重点针对CT校验误差展开研究。首先分析了具有自校功能CT的结构特征,并在此基础上根据CT误差定义对其误差特性进行了理论分析;讨论了影响误差的主要因素;为计算误差大小,建立了基于有限元法瞬态场—路耦合CT误差分析模型;利用该模型分别对CT两种工作模式（测量用和校验用）下的误差进行计算,并与实际测量结果比较。结果表明 ...
吴细秀 +5 more
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Journal of Critical Infrastructure Policy, Volume 7, Issue 1, Spring/Summer 2026.ABSTRACT The National Quality Infrastructure (NQI) in a given country provides the essential framework for quality assurance integrating standardization, metrology, accreditation, and conformity assessment to create the technical backbone for industry and trade. Hence, building a resilient NQI is fundamental to securing medicine quality, enabling local
Addisu Afrassa Tegegne +3 more
wiley +1 more source
六维床在头、胸、腹部肿瘤常规直线加速器放射治疗中的摆位误差回顾性分析
Fushe yanjiu yu fushe gongyi xuebao回顾性分析基于加速器六维床摆位的肿瘤患者的CBCT（Cone-Beam CT，CBCT）图像，比较患者的摆位误差数据，分析肿瘤患者六维床放射治疗中分次内摆位误差的数据，研究六维床对不同位置肿瘤产生的摆位效果差异。选取2020年3月至2023年9月于本中心接受放疗的肿瘤患者85例，分成脑瘤、肺癌、直肠癌和乳腺癌。统计4组患者在左右、头脚、腹背6个自由度（X、Y、Z和Rx、Ry、Rz）的首次和分次内摆位误差。采用双样本异方差t检验对比分析不同瘤种在各个方向上的分次内摆位误差 ...
万 宝 +8 more
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